Characterization of multidrug-resistant Salmonella serovars isolated from meats and human samples in some regions of Jiangsu

Abstract:

A total of 117 Salmonella strains isolated from retail meats and human in some regions of Jiangsu were assayed for their antimicrobial susceptibility, the presence of integrons and antimicrobial resistance genes, and the ability of horizontal transfer of the characterized antimicrobial resistance determinants via conjugation. 111 (94.9%) were resistant to at least two antimicrobial agents. Resistance against streptomycin 92.3% （108/117） was the most common. Whereas 59 (50.4%) were resistant to at least five antimicrobials. Twelve isolates showed resistance to six antimicrobials: ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline, and kanamycin (R type ACSSuTK). A total of 15 different antimicrobial resistance genes were identified in 36 multidrug_resistant Salmonella isolates. While 30 (83%) of these isolates tested carried integrons ranging in size from 0.3 to 1.6 kb. The most common integron was 1.6 kb which carried aadA5 and dfr17 gene cassettes. Conjugation studies demonstrated that there was plasmid_mediated transfer of antimicrobial resistance genes. These data showed that the Salmonella isolates recovered from meats and human in some regions of Jiangsu were commonly resistant to multiple antimicrobials, and genes conferring antimicrobial resistance in Salmonella were often carried on integrons and plasmids and could be transmitted through conjugation. The mobile DNA elements might played very important role in transmission and dissemination of antimicrobial resistance determinants among Salmonella strains.